[PATCH v3 0/2] i2c: Add Loongson-2K0300 I2C controller support

[PATCH v3 0/2] i2c: Add Loongson-2K0300 I2C controller support

[Binbin Zhou]

Hi all:

This patch set describes the I2C controller integrated the
Loongson-2K0300 chip.

It has a significantly different design from the previous I2C
controller(i2c-ls2x), such as support for master-slave transfer mode,
and  DMA transfers (implementation in progress), etc. Therefore, we try
to name it i2c-ls2x-v2.

Thanks.

======
V3:
- Rebase on linux-i2c/i2c-next;
Patch (2/2):
 - Reorder header file follow IWYU principle;
 - Better indentation and coding style;
 - Use generic macro definitions;
 - Amend *all* struct data types;
 - Correct unreasonable variable type definitions;
 - Refact loongson2_i2c_isr_error();
 - of_property_read_u32()->device_property_read_u32();
 - Remove meaningless blank lines and output.

Link to V2:
https://lore.kernel.org/all/cover.1769476820.git.zhoubinbin@loongson.cn/

V2:
Patch (1/2):
 - Add Acked-by tag from Conor, thanks.

Patch (2/2):
 - Reorder the definitions of read() and write();
 - Adjust the calculation method for bus speed.

Link to V1:
https://lore.kernel.org/all/cover.1763018288.git.zhoubinbin@loongson.cn/

Binbin Zhou (2):
  dt-bindings: i2c: loongson,ls2x: Add ls2k0300-i2c compatible
  i2c: ls2x-v2: Add driver for Loongson-2K0300 I2C controller

 .../bindings/i2c/loongson,ls2x-i2c.yaml       |   4 +
 MAINTAINERS                                   |   1 +
 drivers/i2c/busses/Kconfig                    |  10 +
 drivers/i2c/busses/Makefile                   |   1 +
 drivers/i2c/busses/i2c-ls2x-v2.c              | 510 ++++++++++++++++++
 5 files changed, 526 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-ls2x-v2.c


base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
-- 
2.52.0

[PATCH v3 1/2] dt-bindings: i2c: loongson,ls2x: Add ls2k0300-i2c compatible

[Binbin Zhou]

Add "loongson,ls2k0300-i2c" dedicated compatible for representing I2C of
Loongson-2K0300 chip, because its HW integration is quiet different from
others.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
---
 Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml b/Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml
index 67882ec6e06a..ee09c6d9c5f0 100644
--- a/Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml
+++ b/Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml
@@ -16,6 +16,7 @@ properties:
   compatible:
     enum:
       - loongson,ls2k-i2c
+      - loongson,ls2k0300-i2c
       - loongson,ls7a-i2c
 
   reg:
@@ -24,6 +25,9 @@ properties:
   interrupts:
     maxItems: 1
 
+  clocks:
+    maxItems: 1
+
 required:
   - compatible
   - reg
-- 
2.52.0

[PATCH v3 2/2] i2c: ls2x-v2: Add driver for Loongson-2K0300 I2C controller

[Binbin Zhou]

This I2C module is integrated into the Loongson-2K0300 SoCs.

It provides multi-master functionality and controls all I2C bus-specific
timing, protocols, arbitration, and timing. It supports both standard
and fast modes.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
---
 MAINTAINERS                      |   1 +
 drivers/i2c/busses/Kconfig       |  10 +
 drivers/i2c/busses/Makefile      |   1 +
 drivers/i2c/busses/i2c-ls2x-v2.c | 510 +++++++++++++++++++++++++++++++
 4 files changed, 522 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-ls2x-v2.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 55af015174a5..464d00c16b96 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14960,6 +14960,7 @@ M:	Binbin Zhou <zhoubinbin@loongson.cn>
 L:	linux-i2c@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/i2c/loongson,ls2x-i2c.yaml
+F:	drivers/i2c/busses/i2c-ls2x-v2.c
 F:	drivers/i2c/busses/i2c-ls2x.c
 
 LOONGSON PWM DRIVER
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index e11d50750e63..5cad2d0d2569 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -850,6 +850,16 @@ config I2C_LS2X
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-ls2x.
 
+config I2C_LS2X_V2
+	tristate "Loongson-2 Fast Speed I2C adapter"
+	depends on LOONGARCH || COMPILE_TEST
+	help
+	  If you say yes to this option, support will be included for the
+	  I2C interface on the Loongson-2K0300 SoCs.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-ls2x-v2.
+
 config I2C_MLXBF
         tristate "Mellanox BlueField I2C controller"
         depends on (MELLANOX_PLATFORM && ARM64) || COMPILE_TEST
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 547123ab351f..3755c54b3d82 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -80,6 +80,7 @@ obj-$(CONFIG_I2C_KEBA)		+= i2c-keba.o
 obj-$(CONFIG_I2C_KEMPLD)	+= i2c-kempld.o
 obj-$(CONFIG_I2C_LPC2K)		+= i2c-lpc2k.o
 obj-$(CONFIG_I2C_LS2X)		+= i2c-ls2x.o
+obj-$(CONFIG_I2C_LS2X_V2)	+= i2c-ls2x-v2.o
 obj-$(CONFIG_I2C_MESON)		+= i2c-meson.o
 obj-$(CONFIG_I2C_MICROCHIP_CORE)	+= i2c-microchip-corei2c.o
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
diff --git a/drivers/i2c/busses/i2c-ls2x-v2.c b/drivers/i2c/busses/i2c-ls2x-v2.c
new file mode 100644
index 000000000000..36017354803d
--- /dev/null
+++ b/drivers/i2c/busses/i2c-ls2x-v2.c
@@ -0,0 +1,510 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Loongson-2K0300 I2C controller driver
+ *
+ * Copyright (C) 2025-2026 Loongson Technology Corporation Limited
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+/* Loongson-2 fast I2C offset registers */
+#define LOONGSON2_I2C_CR1	0x00	/* I2C control 1 register */
+#define LOONGSON2_I2C_CR2	0x04	/* I2C control 2 register */
+#define LOONGSON2_I2C_OAR	0x08	/* I2C slave address register */
+#define LOONGSON2_I2C_DR	0x10	/* I2C data register */
+#define LOONGSON2_I2C_SR1	0x14	/* I2C status 1 register */
+#define LOONGSON2_I2C_SR2	0x18	/* I2C status 2 register */
+#define LOONGSON2_I2C_CCR	0x1c	/* I2C clock control register */
+#define LOONGSON2_I2C_TRISE	0x20	/* I2C trise register */
+#define LOONGSON2_I2C_FLTR	0x24
+
+/* Bitfields of I2C control 1 register */
+#define LOONGSON2_I2C_CR1_PE		BIT(0)
+#define LOONGSON2_I2C_CR1_START		BIT(8)
+#define LOONGSON2_I2C_CR1_STOP		BIT(9)
+#define LOONGSON2_I2C_CR1_ACK		BIT(10)
+#define LOONGSON2_I2C_CR1_POS		BIT(11)
+
+#define LOONGSON2_I2C_CR1_OP_MASK	(LOONGSON2_I2C_CR1_START | LOONGSON2_I2C_CR1_STOP)
+
+/* Bitfields of I2C control 2 register */
+#define LOONGSON2_I2C_CR2_FREQ		GENMASK(5, 0)	/* APB Clock Frequency in MHz */
+#define LOONGSON2_I2C_CR2_ITERREN	BIT(8)	/* Fault-Class Interrupt Enable */
+#define LOONGSON2_I2C_CR2_ITEVTEN	BIT(9)	/* Event-Based Interrupt Enable */
+#define LOONGSON2_I2C_CR2_ITBUFEN	BIT(10)	/* Cache-Class Interrupt Enable */
+
+#define LOONGSON2_I2C_CR2_INT_MASK	\
+	(LOONGSON2_I2C_CR2_ITBUFEN | LOONGSON2_I2C_CR2_ITEVTEN | LOONGSON2_I2C_CR2_ITERREN)
+
+/* Bitfields of I2C status 1 register */
+#define LOONGSON2_I2C_SR1_SB		BIT(0)
+#define LOONGSON2_I2C_SR1_ADDR		BIT(1)
+#define LOONGSON2_I2C_SR1_BTF		BIT(2)
+#define LOONGSON2_I2C_SR1_RXNE		BIT(6)
+#define LOONGSON2_I2C_SR1_TXE		BIT(7)
+#define LOONGSON2_I2C_SR1_BERR		BIT(8)
+#define LOONGSON2_I2C_SR1_ARLO		BIT(9)
+#define LOONGSON2_I2C_SR1_AF		BIT(10)
+
+#define LOONGSON2_I2C_SR1_ITEVTEN_MASK	\
+	(LOONGSON2_I2C_SR1_BTF | LOONGSON2_I2C_SR1_ADDR | LOONGSON2_I2C_SR1_SB)
+#define LOONGSON2_I2C_SR1_ITBUFEN_MASK	(LOONGSON2_I2C_SR1_TXE | LOONGSON2_I2C_SR1_RXNE)
+#define LOONGSON2_I2C_SR1_ITERREN_MASK	\
+	(LOONGSON2_I2C_SR1_AF | LOONGSON2_I2C_SR1_ARLO | LOONGSON2_I2C_SR1_BERR)
+
+/* Bitfields of I2C status 2 register */
+#define LOONGSON2_I2C_SR2_BUSY		BIT(1)
+
+/* Bitfields of I2C clock control register */
+#define LOONGSON2_I2C_CCR_CCR		GENMASK(11, 0)
+#define LOONGSON2_I2C_CCR_DUTY		BIT(14)
+#define LOONGSON2_I2C_CCR_FS		BIT(15)
+
+/* Bitfields of I2C trise register */
+#define LOONGSON2_I2C_TRISE_SCL		GENMASK(5, 0)
+
+#define LOONGSON2_I2C_FREE_SLEEP_US	(1 * USEC_PER_MSEC)
+#define LOONGSON2_I2C_FREE_TIMEOUT_US	(5 * USEC_PER_MSEC)
+
+/**
+ * struct loongson2_i2c_msg - client specific data
+ * @buf: data buffer
+ * @count: number of bytes to be transferred
+ * @result: result of the transfer
+ * @addr: 8-bit slave addr, including r/w bit
+ * @stop: last I2C msg to be sent, i.e. STOP to be generated
+ */
+struct loongson2_i2c_msg {
+	u8	*buf;
+	u32	count;
+	int	result;
+	u8      addr;
+	bool	stop;
+};
+
+/**
+ * struct loongson2_i2c_priv - private data of the controller
+ * @adapter: I2C adapter for this controller
+ * @clk: hw i2c clock
+ * @complete: completion of I2C message
+ * @regmap: regmap of the I2C device
+ * @speed: I2C clock frequency of the controller. Standard or Fast are supported
+ * @parent_rate: I2C clock parent rate in MHz
+ * @msg: I2C transfer information
+ */
+struct loongson2_i2c_priv {
+	struct i2c_adapter		adapter;
+	struct completion		complete;
+	struct clk			*clk;
+	struct regmap			*regmap;
+	int				speed;
+	int				parent_rate;
+	struct loongson2_i2c_msg	msg;
+};
+
+static void loongson2_i2c_disable_irq(struct loongson2_i2c_priv *priv)
+{
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_INT_MASK, 0);
+}
+
+static void loongson2_i2c_read_msg(struct loongson2_i2c_priv *priv)
+{
+	struct loongson2_i2c_msg *msg = &priv->msg;
+	u32 rbuf;
+
+	regmap_read(priv->regmap, LOONGSON2_I2C_DR, &rbuf);
+	*msg->buf++ = rbuf;
+	msg->count--;
+}
+
+static void loongson2_i2c_write_msg(struct loongson2_i2c_priv *priv, u8 byte)
+{
+	regmap_write(priv->regmap, LOONGSON2_I2C_DR, byte);
+}
+
+static void loongson2_i2c_terminate_xfer(struct loongson2_i2c_priv *priv)
+{
+	struct loongson2_i2c_msg *msg = &priv->msg;
+
+	loongson2_i2c_disable_irq(priv);
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_OP_MASK,
+			   msg->stop ? LOONGSON2_I2C_CR1_STOP : LOONGSON2_I2C_CR1_START);
+	complete(&priv->complete);
+}
+
+static void loongson2_i2c_handle_read(struct loongson2_i2c_priv *priv, int flag)
+{
+	struct loongson2_i2c_msg *msg = &priv->msg;
+	unsigned int i;
+	bool changed;
+
+	switch (msg->count) {
+	case 1:
+		/* only transmit 1 bytes condition */
+		loongson2_i2c_disable_irq(priv);
+		loongson2_i2c_read_msg(priv);
+		complete(&priv->complete);
+		break;
+	case 2:
+		if (flag != 1) {
+			/* ensure only transmit 2 bytes condition */
+			regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
+					   LOONGSON2_I2C_CR2_ITBUFEN, 0);
+			break;
+		}
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_OP_MASK,
+				   msg->stop ? LOONGSON2_I2C_CR1_STOP : LOONGSON2_I2C_CR1_START);
+
+		loongson2_i2c_disable_irq(priv);
+
+		for (i = msg->count; i > 0; i--)
+			loongson2_i2c_read_msg(priv);
+
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_POS, 0);
+		complete(&priv->complete);
+		break;
+	case 3:
+		regmap_update_bits_check(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_ITBUFEN,
+					 0, &changed);
+		if (changed)
+			break;
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_ACK, 0);
+		fallthrough;
+	default:
+		loongson2_i2c_read_msg(priv);
+	}
+}
+
+static void loongson2_i2c_handle_write(struct loongson2_i2c_priv *priv)
+{
+	struct loongson2_i2c_msg *msg = &priv->msg;
+
+	if (msg->count) {
+		loongson2_i2c_write_msg(priv, *msg->buf++);
+		msg->count--;
+		if (!msg->count)
+			regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
+					   LOONGSON2_I2C_CR2_ITBUFEN, 0);
+	} else {
+		loongson2_i2c_terminate_xfer(priv);
+	}
+}
+
+static void loongson2_i2c_handle_rx_addr(struct loongson2_i2c_priv *priv)
+{
+	struct loongson2_i2c_msg *msg = &priv->msg;
+
+	switch (msg->count) {
+	case 0:
+		loongson2_i2c_terminate_xfer(priv);
+		break;
+	case 1:
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1,
+				   LOONGSON2_I2C_CR1_ACK | LOONGSON2_I2C_CR1_POS, 0);
+		/* start or stop */
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_OP_MASK,
+				   msg->stop ? LOONGSON2_I2C_CR1_STOP : LOONGSON2_I2C_CR1_START);
+		break;
+	case 2:
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_ACK, 0);
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_POS,
+				   LOONGSON2_I2C_CR1_POS);
+		break;
+
+	default:
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_ACK,
+				   LOONGSON2_I2C_CR1_ACK);
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_POS, 0);
+	}
+}
+
+static void loongson2_i2c_isr_error(u32 status, void *data)
+{
+	struct loongson2_i2c_priv *priv = data;
+	struct loongson2_i2c_msg *msg = &priv->msg;
+
+	/* Arbitration lost */
+	if (status & LOONGSON2_I2C_SR1_ARLO) {
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_SR1, LOONGSON2_I2C_SR1_ARLO, 0);
+		msg->result = -EAGAIN;
+		goto out;
+	}
+
+	/*
+	 * Acknowledge failure:
+	 * In master transmitter mode a Stop must be generated by software
+	 */
+	if (status & LOONGSON2_I2C_SR1_AF) {
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_STOP,
+				   LOONGSON2_I2C_CR1_STOP);
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_SR1, LOONGSON2_I2C_SR1_AF, 0);
+		msg->result = -EIO;
+		goto out;
+	}
+
+	/* Bus error */
+	if (status & LOONGSON2_I2C_SR1_BERR) {
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_SR1, LOONGSON2_I2C_SR1_BERR, 0);
+		msg->result = -EIO;
+		goto out;
+	}
+
+out:
+	loongson2_i2c_disable_irq(priv);
+	complete(&priv->complete);
+}
+
+static irqreturn_t loongson2_i2c_isr_event(int irq, void *data)
+{
+	struct loongson2_i2c_priv *priv = data;
+	struct device *dev = priv->adapter.dev.parent;
+	struct loongson2_i2c_msg *msg = &priv->msg;
+	u32 status, ien, event, cr2, possible_status;
+
+	regmap_read(priv->regmap, LOONGSON2_I2C_SR1, &status);
+	if (status & LOONGSON2_I2C_SR1_ITERREN_MASK) {
+		loongson2_i2c_isr_error(status, data);
+		return IRQ_NONE;
+	}
+
+	regmap_read(priv->regmap, LOONGSON2_I2C_CR2, &cr2);
+	ien = cr2 & LOONGSON2_I2C_CR2_INT_MASK;
+
+	/* Update possible_status if buffer interrupt is enabled */
+	possible_status = LOONGSON2_I2C_SR1_ITEVTEN_MASK;
+	if (ien & LOONGSON2_I2C_CR2_ITBUFEN)
+		possible_status |= LOONGSON2_I2C_SR1_ITBUFEN_MASK;
+
+	event = status & possible_status;
+	if (!event) {
+		dev_dbg(dev, "spurious evt irq (status=0x%08x, ien=0x%08x)\n", status, ien);
+		return IRQ_NONE;
+	}
+
+	/* Start condition generated */
+	if (event & LOONGSON2_I2C_SR1_SB)
+		loongson2_i2c_write_msg(priv, msg->addr);
+
+	/* I2C Address sent */
+	if (event & LOONGSON2_I2C_SR1_ADDR) {
+		if (msg->addr & I2C_M_RD)
+			loongson2_i2c_handle_rx_addr(priv);
+		/* Clear ADDR flag */
+		regmap_read(priv->regmap, LOONGSON2_I2C_SR2, &status);
+		/* Enable buffer interrupts for RX/TX not empty events */
+		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_ITBUFEN,
+				   LOONGSON2_I2C_CR2_ITBUFEN);
+	}
+
+	if (msg->addr & I2C_M_RD) {
+		/* RX not empty */
+		if (event & LOONGSON2_I2C_SR1_RXNE)
+			loongson2_i2c_handle_read(priv, 0);
+
+		if (event & LOONGSON2_I2C_SR1_BTF)
+			loongson2_i2c_handle_read(priv, 1);
+	} else {
+		/* TX empty */
+		if (event & LOONGSON2_I2C_SR1_TXE)
+			loongson2_i2c_handle_write(priv);
+
+		if (event & LOONGSON2_I2C_SR1_BTF)
+			loongson2_i2c_handle_write(priv);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int loongson2_i2c_xfer_msg(struct loongson2_i2c_priv *priv, struct i2c_msg *msg,
+				  bool is_stop)
+{
+	struct loongson2_i2c_msg *l_msg = &priv->msg;
+	unsigned long timeout;
+
+	l_msg->addr   = i2c_8bit_addr_from_msg(msg);
+	l_msg->buf    = msg->buf;
+	l_msg->count  = msg->len;
+	l_msg->stop   = is_stop;
+	l_msg->result = 0;
+
+	reinit_completion(&priv->complete);
+
+	/* Enable events and errors interrupts */
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
+			   LOONGSON2_I2C_CR2_ITEVTEN | LOONGSON2_I2C_CR2_ITERREN,
+			   LOONGSON2_I2C_CR2_ITEVTEN | LOONGSON2_I2C_CR2_ITERREN);
+
+	timeout = wait_for_completion_timeout(&priv->complete, priv->adapter.timeout);
+	if (!timeout)
+		return -ETIMEDOUT;
+
+	return l_msg->result;
+}
+
+static int loongson2_i2c_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[], int num)
+{
+	struct loongson2_i2c_priv *priv = i2c_get_adapdata(i2c_adap);
+	struct device *dev = priv->adapter.dev.parent;
+	unsigned int i, status;
+	int ret;
+
+	/* Wait I2C bus free */
+	ret = regmap_read_poll_timeout(priv->regmap, LOONGSON2_I2C_SR2, status,
+				       !(status & LOONGSON2_I2C_SR2_BUSY),
+				       LOONGSON2_I2C_FREE_SLEEP_US,
+				       LOONGSON2_I2C_FREE_TIMEOUT_US);
+	if (ret) {
+		dev_dbg(dev, "The I2C bus is busy now.\n");
+		return ret;
+	}
+
+	/* Start generation */
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_START,
+			   LOONGSON2_I2C_CR1_START);
+
+	for (i = 0; i < num; i++) {
+		ret = loongson2_i2c_xfer_msg(priv, &msgs[i], i == num - 1);
+		if (ret < 0)
+			return ret;
+	}
+
+	return num;
+}
+
+static u32 loongson2_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm loongson2_i2c_algo = {
+	.xfer		= loongson2_i2c_xfer,
+	.functionality	= loongson2_i2c_func,
+};
+
+static int loongson2_i2c_adjust_bus_speed(struct loongson2_i2c_priv *priv)
+{
+	u32 val, freq_mhz, ccr;
+
+	priv->parent_rate = clk_get_rate(priv->clk);
+	freq_mhz = DIV_ROUND_UP(priv->parent_rate, HZ_PER_MHZ);
+
+	if (priv->speed == I2C_MAX_STANDARD_MODE_FREQ) {
+		 /* Select Standard mode */
+		ccr = 0;
+		val = DIV_ROUND_UP(priv->parent_rate, I2C_MAX_STANDARD_MODE_FREQ * 2);
+	} else {
+		/* Select Fast mode */
+		ccr = LOONGSON2_I2C_CCR_FS;
+		val = DIV_ROUND_UP(priv->parent_rate, I2C_MAX_FAST_MODE_FREQ * 3);
+	}
+
+	FIELD_MODIFY(LOONGSON2_I2C_CCR_CCR, &ccr, val);
+	regmap_write(priv->regmap, LOONGSON2_I2C_CCR, ccr);
+
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_FREQ,
+			   FIELD_GET(LOONGSON2_I2C_CR2_FREQ, freq_mhz));
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_TRISE, LOONGSON2_I2C_TRISE_SCL,
+			   LOONGSON2_I2C_TRISE_SCL);
+
+	/* Enable I2C */
+	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_PE,
+			   LOONGSON2_I2C_CR1_PE);
+
+	return 0;
+}
+
+static const struct regmap_config loongson2_i2c_regmap_config = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.max_register = LOONGSON2_I2C_TRISE,
+};
+
+static int loongson2_i2c_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct loongson2_i2c_priv *priv;
+	struct i2c_adapter *adap;
+	void __iomem *base;
+	u32 clk_rate;
+	int irq, ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	priv->regmap = devm_regmap_init_mmio(dev, base, &loongson2_i2c_regmap_config);
+	if (IS_ERR(priv->regmap))
+		return dev_err_probe(dev, PTR_ERR(priv->regmap), "Failed to init regmap.\n");
+
+	priv->clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(dev, PTR_ERR(priv->clk), "Failed to enable clock.\n");
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	adap = &priv->adapter;
+	adap->retries = 5;
+	adap->nr = pdev->id;
+	adap->dev.parent = dev;
+	adap->owner = THIS_MODULE;
+	adap->algo = &loongson2_i2c_algo;
+	adap->timeout = 2 * HZ;
+	device_set_node(&adap->dev, dev_fwnode(dev));
+	i2c_set_adapdata(adap, priv);
+	strscpy(adap->name, pdev->name);
+	init_completion(&priv->complete);
+	platform_set_drvdata(pdev, priv);
+
+	priv->speed = I2C_MAX_STANDARD_MODE_FREQ;
+	ret = device_property_read_u32(dev, "clock-frequency", &clk_rate);
+	if (!ret && clk_rate >= I2C_MAX_FAST_MODE_FREQ)
+		priv->speed = I2C_MAX_FAST_MODE_FREQ;
+
+	ret = loongson2_i2c_adjust_bus_speed(priv);
+	if (ret)
+		return ret;
+
+	ret = devm_request_irq(dev, irq, loongson2_i2c_isr_event, IRQF_SHARED, pdev->name, priv);
+	if (ret)
+		return ret;
+
+	return devm_i2c_add_adapter(dev, adap);
+}
+
+static const struct of_device_id loongson2_i2c_id_table[] = {
+	{ .compatible = "loongson,ls2k0300-i2c" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, loongson2_i2c_id_table);
+
+static struct platform_driver loongson2_i2c_driver = {
+	.driver = {
+		.name = "loongson2-i2c-v2",
+		.of_match_table = loongson2_i2c_id_table,
+	},
+	.probe = loongson2_i2c_probe,
+};
+module_platform_driver(loongson2_i2c_driver);
+
+MODULE_DESCRIPTION("Loongson-2K0300 I2C bus driver");
+MODULE_AUTHOR("Loongson Technology Corporation Limited");
+MODULE_LICENSE("GPL");
-- 
2.52.0

Re: [PATCH v3 2/2] i2c: ls2x-v2: Add driver for Loongson-2K0300 I2C controller

[Andy Shevchenko]

On Wed, Feb 25, 2026 at 03:34:44PM +0800, Binbin Zhou wrote:
> This I2C module is integrated into the Loongson-2K0300 SoCs.
> 
> It provides multi-master functionality and controls all I2C bus-specific
> timing, protocols, arbitration, and timing. It supports both standard
> and fast modes.

...

> +struct loongson2_i2c_priv {
> +	struct i2c_adapter		adapter;
> +	struct completion		complete;
> +	struct clk			*clk;
> +	struct regmap			*regmap;

> +	int				speed;
> +	int				parent_rate;

May any of these two be negative? The kernel doc says nothing about that.

> +	struct loongson2_i2c_msg	msg;
> +};

...

> +static void loongson2_i2c_handle_read(struct loongson2_i2c_priv *priv, int flag)
> +{
> +	struct loongson2_i2c_msg *msg = &priv->msg;
> +	unsigned int i;
> +	bool changed;
> +
> +	switch (msg->count) {
> +	case 1:
> +		/* only transmit 1 bytes condition */
> +		loongson2_i2c_disable_irq(priv);
> +		loongson2_i2c_read_msg(priv);
> +		complete(&priv->complete);
> +		break;
> +	case 2:
> +		if (flag != 1) {
> +			/* ensure only transmit 2 bytes condition */
> +			regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
> +					   LOONGSON2_I2C_CR2_ITBUFEN, 0);
> +			break;
> +		}
> +		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_OP_MASK,
> +				   msg->stop ? LOONGSON2_I2C_CR1_STOP : LOONGSON2_I2C_CR1_START);
> +
> +		loongson2_i2c_disable_irq(priv);
> +
> +		for (i = msg->count; i > 0; i--)
> +			loongson2_i2c_read_msg(priv);
> +
> +		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_POS, 0);
> +		complete(&priv->complete);
> +		break;
> +	case 3:
> +		regmap_update_bits_check(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_ITBUFEN,
> +					 0, &changed);
> +		if (changed)
> +			break;
> +		regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_ACK, 0);
> +		fallthrough;

Instead better to spell it explicitly:

		loongson2_i2c_read_msg(priv);
		break;

> +	default:
> +		loongson2_i2c_read_msg(priv);

Missing break.

> +	}
> +}

This also make me think for the possible optimisations.
if regmap_updates_bit() in case 2 can be run after the completion,
the case 1 with a parameter may be split to a helper.

Also would be nice to have a comment why in case 3 we only read a single
message.

...

> +static void loongson2_i2c_handle_write(struct loongson2_i2c_priv *priv)
> +{
> +	struct loongson2_i2c_msg *msg = &priv->msg;
> +
> +	if (msg->count) {
> +		loongson2_i2c_write_msg(priv, *msg->buf++);

> +		msg->count--;
> +		if (!msg->count)

Can be

		if (!--msg->count)

but someone may find it difficult to correctly parse.

> +			regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
> +					   LOONGSON2_I2C_CR2_ITBUFEN, 0);
> +	} else {
> +		loongson2_i2c_terminate_xfer(priv);
> +	}
> +}

...

> +static int loongson2_i2c_adjust_bus_speed(struct loongson2_i2c_priv *priv)
> +{
> +	u32 val, freq_mhz, ccr;
> +
> +	priv->parent_rate = clk_get_rate(priv->clk);

> +	freq_mhz = DIV_ROUND_UP(priv->parent_rate, HZ_PER_MHZ);

Usually the rule of thumb to put assignments close to its first user...

> +	if (priv->speed == I2C_MAX_STANDARD_MODE_FREQ) {
> +		 /* Select Standard mode */
> +		ccr = 0;
> +		val = DIV_ROUND_UP(priv->parent_rate, I2C_MAX_STANDARD_MODE_FREQ * 2);
> +	} else {
> +		/* Select Fast mode */
> +		ccr = LOONGSON2_I2C_CCR_FS;
> +		val = DIV_ROUND_UP(priv->parent_rate, I2C_MAX_FAST_MODE_FREQ * 3);
> +	}
> +
> +	FIELD_MODIFY(LOONGSON2_I2C_CCR_CCR, &ccr, val);
> +	regmap_write(priv->regmap, LOONGSON2_I2C_CCR, ccr);

...somewhere here.

> +	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_FREQ,
> +			   FIELD_GET(LOONGSON2_I2C_CR2_FREQ, freq_mhz));
> +	regmap_update_bits(priv->regmap, LOONGSON2_I2C_TRISE, LOONGSON2_I2C_TRISE_SCL,
> +			   LOONGSON2_I2C_TRISE_SCL);
> +
> +	/* Enable I2C */
> +	regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_PE,
> +			   LOONGSON2_I2C_CR1_PE);
> +
> +	return 0;
> +}

...

> +	priv->speed = I2C_MAX_STANDARD_MODE_FREQ;
> +	ret = device_property_read_u32(dev, "clock-frequency", &clk_rate);
> +	if (!ret && clk_rate >= I2C_MAX_FAST_MODE_FREQ)
> +		priv->speed = I2C_MAX_FAST_MODE_FREQ;

Please, use i2c_parse_fw_timings() instead of custom approach.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 2/2] i2c: ls2x-v2: Add driver for Loongson-2K0300 I2C controller

[Binbin Zhou]

Hi Andy:

Sorry for the late reply.

On Wed, Feb 25, 2026 at 6:06 PM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Wed, Feb 25, 2026 at 03:34:44PM +0800, Binbin Zhou wrote:
> > This I2C module is integrated into the Loongson-2K0300 SoCs.
> >
> > It provides multi-master functionality and controls all I2C bus-specific
> > timing, protocols, arbitration, and timing. It supports both standard
> > and fast modes.
>
> ...
>
> > +struct loongson2_i2c_priv {
> > +     struct i2c_adapter              adapter;
> > +     struct completion               complete;
> > +     struct clk                      *clk;
> > +     struct regmap                   *regmap;
>
> > +     int                             speed;
> > +     int                             parent_rate;
>
> May any of these two be negative? The kernel doc says nothing about that.

It should be:

u32 speed;
unsigned long parent_rate;
>
> > +     struct loongson2_i2c_msg        msg;
> > +};
>
> ...
>
> > +static void loongson2_i2c_handle_read(struct loongson2_i2c_priv *priv, int flag)
> > +{
> > +     struct loongson2_i2c_msg *msg = &priv->msg;
> > +     unsigned int i;
> > +     bool changed;
> > +
> > +     switch (msg->count) {
> > +     case 1:
> > +             /* only transmit 1 bytes condition */
> > +             loongson2_i2c_disable_irq(priv);
> > +             loongson2_i2c_read_msg(priv);
> > +             complete(&priv->complete);
> > +             break;
> > +     case 2:
> > +             if (flag != 1) {
> > +                     /* ensure only transmit 2 bytes condition */
> > +                     regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
> > +                                        LOONGSON2_I2C_CR2_ITBUFEN, 0);
> > +                     break;
> > +             }
> > +             regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_OP_MASK,
> > +                                msg->stop ? LOONGSON2_I2C_CR1_STOP : LOONGSON2_I2C_CR1_START);
> > +
> > +             loongson2_i2c_disable_irq(priv);
> > +
> > +             for (i = msg->count; i > 0; i--)
> > +                     loongson2_i2c_read_msg(priv);
> > +
> > +             regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_POS, 0);
> > +             complete(&priv->complete);
> > +             break;
> > +     case 3:
> > +             regmap_update_bits_check(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_ITBUFEN,
> > +                                      0, &changed);
> > +             if (changed)
> > +                     break;
> > +             regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_ACK, 0);
> > +             fallthrough;
>
> Instead better to spell it explicitly:
>
>                 loongson2_i2c_read_msg(priv);
>                 break;
>
> > +     default:
> > +             loongson2_i2c_read_msg(priv);
>
> Missing break.
>
> > +     }
> > +}
>
> This also make me think for the possible optimisations.
> if regmap_updates_bit() in case 2 can be run after the completion,
> the case 1 with a parameter may be split to a helper.
>
> Also would be nice to have a comment why in case 3 we only read a single
> message.

This part might be a bit confusing. I'll try to restructure it, which
might make it clearer.

In `loongson2_i2c_isr_event()`, the read/write operations are divided
into three parts.

        /* TX empty */
        if ((event & LOONGSON2_I2C_SR1_TXE) && !(msg->addr & I2C_M_RD))
                loongson2_i2c_handle_write(priv);

        /* RX not empty */
        if ((event & LOONGSON2_I2C_SR1_RXNE) && (msg->addr & I2C_M_RD))
                loongson2_i2c_handle_read(priv);
//Handle FIFO empty interrupt in case of read, it is called when a new
data is received in data register

        /*
         * The BTF (Byte Transfer finished) event occurs
         */
        if (event & LOONGSON2_I2C_SR1_BTF) {
                if (msg->addr & I2C_M_RD)
                        loongson2_i2c_handle_rx_done(priv);
//Handle byte transfer finished interrupt in case of read
                else
                        loongson2_i2c_handle_write(priv);
        }


static void loongson2_i2c_handle_read(struct loongson2_i2c_priv *priv)
{
        struct loongson2_i2c_msg *msg = &priv->msg;

        switch (msg->count) {
        case 1:
                loongson2_i2c_disable_irq(priv);
                loongson2_i2c_read_msg(priv);
                complete(&priv->complete);
                break;
        case 2:
        case 3:
                /*
                 * For 2-byte/3-byte reception and for N-byte
reception with N > 3, we have to
                 * wait for byte transferred finished event before reading data.
                 * Just disable buffer interrupt in order to avoid
another system preemption due
                 * to RX not empty event.
                 */
                regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
LOONGSON2_I2C_CR2_ITBUFEN, 0);
                break;
        default:
                /*
                 * For N byte reception with N > 3 we directly read
data register
                 * until N-2 data.
                 */
                loongson2_i2c_read_msg(priv);
                break;
        }
}

static void loongson2_i2c_handle_rx_done(struct loongson2_i2c_priv *priv)
{
        struct loongson2_i2c_msg *msg = &priv->msg;
        u32 i;

        switch (msg->count) {
        case 2:
                /*
                 * The STOP/START bit has to be set before reading the
last two bytes.
                 * After that, we could read the last two bytes.
                 */
                regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1,
LOONGSON2_I2C_CR1_OP_MASK,
                                   msg->stop ? LOONGSON2_I2C_CR1_STOP
: LOONGSON2_I2C_CR1_START);

                for (i = 2; i > 0; i--)
                        loongson2_i2c_read_msg(priv);

                loongson2_i2c_disable_irq(priv);
                complete(&priv->complete);
                break;
        case 3:
                /*
                 * In order to generate the NACK after the last
received data byte, enable NACK
                 * before reading N-2 data
                 */
                regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1,
LOONGSON2_I2C_CR1_ACK, 0);
                loongson2_i2c_read_msg(priv);
                break;
        default:
                loongson2_i2c_read_msg(priv);
                break;
        }
}

>
> ...
>
> > +static void loongson2_i2c_handle_write(struct loongson2_i2c_priv *priv)
> > +{
> > +     struct loongson2_i2c_msg *msg = &priv->msg;
> > +
> > +     if (msg->count) {
> > +             loongson2_i2c_write_msg(priv, *msg->buf++);
>
> > +             msg->count--;
> > +             if (!msg->count)
>
> Can be
>
>                 if (!--msg->count)
>
> but someone may find it difficult to correctly parse.
>
> > +                     regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
> > +                                        LOONGSON2_I2C_CR2_ITBUFEN, 0);
> > +     } else {
> > +             loongson2_i2c_terminate_xfer(priv);
> > +     }
> > +}
>
> ...
>
> > +static int loongson2_i2c_adjust_bus_speed(struct loongson2_i2c_priv *priv)
> > +{
> > +     u32 val, freq_mhz, ccr;
> > +
> > +     priv->parent_rate = clk_get_rate(priv->clk);
>
> > +     freq_mhz = DIV_ROUND_UP(priv->parent_rate, HZ_PER_MHZ);
>
> Usually the rule of thumb to put assignments close to its first user...

See blow.
>
> > +     if (priv->speed == I2C_MAX_STANDARD_MODE_FREQ) {
> > +              /* Select Standard mode */
> > +             ccr = 0;
> > +             val = DIV_ROUND_UP(priv->parent_rate, I2C_MAX_STANDARD_MODE_FREQ * 2);
> > +     } else {
> > +             /* Select Fast mode */
> > +             ccr = LOONGSON2_I2C_CCR_FS;
> > +             val = DIV_ROUND_UP(priv->parent_rate, I2C_MAX_FAST_MODE_FREQ * 3);
> > +     }
> > +
> > +     FIELD_MODIFY(LOONGSON2_I2C_CCR_CCR, &ccr, val);
> > +     regmap_write(priv->regmap, LOONGSON2_I2C_CCR, ccr);
>
> ...somewhere here.
>
> > +     regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2, LOONGSON2_I2C_CR2_FREQ,
> > +                        FIELD_GET(LOONGSON2_I2C_CR2_FREQ, freq_mhz));
> > +     regmap_update_bits(priv->regmap, LOONGSON2_I2C_TRISE, LOONGSON2_I2C_TRISE_SCL,
> > +                        LOONGSON2_I2C_TRISE_SCL);
> > +
> > +     /* Enable I2C */
> > +     regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR1, LOONGSON2_I2C_CR1_PE,
> > +                        LOONGSON2_I2C_CR1_PE);
> > +
> > +     return 0;
> > +}
>
> ...
>
> > +     priv->speed = I2C_MAX_STANDARD_MODE_FREQ;
> > +     ret = device_property_read_u32(dev, "clock-frequency", &clk_rate);
> > +     if (!ret && clk_rate >= I2C_MAX_FAST_MODE_FREQ)
> > +             priv->speed = I2C_MAX_FAST_MODE_FREQ;
>
> Please, use i2c_parse_fw_timings() instead of custom approach.

This section will be merged into `loongson2_i2c_adjust_bus_speed()`,
and `bus_freq_hz` will replace `priv->speed` as follows:

static int loongson2_i2c_adjust_bus_speed(struct loongson2_i2c_priv *priv)
{
        struct i2c_timings i2c_t;
        ....

        i2c_parse_fw_timings(dev, &i2c_t, true);
        priv->parent_rate = clk_get_rate(priv->clk);

        if (i2c_t.bus_freq_hz == I2C_MAX_STANDARD_MODE_FREQ) {
                 /* Select Standard mode */
                ccr = 0;
                val = DIV_ROUND_UP(priv->parent_rate, i2c_t.bus_freq_hz * 2);
        } else if (i2c_t.bus_freq_hz == I2C_MAX_FAST_MODE_FREQ) {
                /* Select Fast mode */
                ccr = LOONGSON2_I2C_CCR_FS;
                val = DIV_ROUND_UP(priv->parent_rate, i2c_t.bus_freq_hz * 3);
        } else {
                dev_err(dev, "Unsupported speed (%uhz)\n", i2c_t.bus_freq_hz);
                return -EINVAL;
        }

......
        freq_mhz = DIV_ROUND_UP(priv->parent_rate, HZ_PER_MHZ);
        regmap_update_bits(priv->regmap, LOONGSON2_I2C_CR2,
LOONGSON2_I2C_CR2_FREQ,
                           FIELD_GET(LOONGSON2_I2C_CR2_FREQ, freq_mhz));
.............

        return 0;
}

>
> --
> With Best Regards,
> Andy Shevchenko
>
>

--
Thanks.
Binbin